Hemorrhoids are dilated veins which occur in and around the anus and rectum. They may be external or internal, which means they may be visible and felt or not. A common cause of Hemorrhoids is the standing position, in which all of the blood above the rectum exerts pressure on the rectal and anus areas. Other conditions that contribute include: poor bowel habits, constipation, diarrhea, pregnancy, obesity, and frequent straining during bowel movements.